Drilling machine



May 23, 1939. R. K. JEFFREY DRILLING IACHINB Original vFiled May 14,1934 5 Sheets-Sheet l m M M.

AT'T'Y R. K. JEFFREY DRILLING IACHINE y Original Filed lay 14, 1954 5Sheets-Sheet' 2 May 23, 1939. R. K; JEFFREY DRILLING MACHINE OriginalFiled lay 14, 1934 /NVENTOR Rober-7" /f Jeff/*eyl ATT'Y May 23, 1939. R.K. JEFFREY 2,159,087

DRILLING IACHINE v 'Original Filed lay 14, 1934 5 Sheets-Sheet 4 'Ell.73I f @bmw-MM.

Patented May 23, 1939 UNITED STATES PATENT f OFFICE Company, a corpora-Application May 14, 1934, Serial No. 725,504

, Renewed Octo ,26, 1938 .-7 Claims. (Cl. 172-46) 'lhe present inventionrelates to portable drilling units of the manually supported type andalthough particularly adapted for use in drilling operations in coalmines, it may have a general application.

One of the objects of the present invention is the provision of improvedand eilicient mechavnism for a portable manually supported drillingmachine to reduce the weight thereof to a minimum,-

More particularly it is the object of the present invention to provide adrilling machine sutilciently light in weight to enable it to beeiiciently handled by a single operator without necessitatl5 ingmounting of the drilling machine on any support.

Another object of the invention is the provision of drill operatingmechanism compactly ar- 'ranged in a dame-proof casing in a drillingma.-

chine capable of being manually supported during operation. g

Another object of the invention is the provision of controllingmechanism for the motor of a drilling machine, operable by means of a.lifting handle to eect starting of the machine, combined with means forautomatically stopping the machine upon release of the handle.`

A further object of the invention is the provision of improved andefficient electric switch mechanism for controlling an electric motor ofa drilling machine, including means for holding the switch closed untilopened with a snap action to reduce the arcing to a'minimum.

A still further object of the invention is to provide a portablemanually supported drilling machine with the center of gravity placedbehind the axis of lifting handles to effect such counterbalancing ofthe weights of the parts of themachine as to facilitate free handlingoi' the machine. Another object of the invention is the provision ofimproved and emcient air circulating mechanism about the operating motorof a drilling machine within an enclosing casing to increase the heatradiating capacity of thelatter and thereby eil'ect cooling of the motorto prevent overheating thereof during operation ofthe drilling machine.

Other objects of the invention will appear hereinafter, the novelfeatures and combinations being set forth in the appended claims.

In the accompanying drawings: Fig. l is a plan view of my improveddrilling machine with a drill connected thereto in drilling position;

Fig. 2 is an elevational view taken on the line 2 2 of F18. 1 with thedrill removed from its socket and the cover for the switch housingremoved to show in elevation the electric switch for controlling theoperating motor;

Fig. 3 is a view taken on the line 3 3 of Fig. 2, looking in thedirection of the arrows; showing mechanism for clamping to thelcasing ofa machine a power cable of electric wires leading from the source ofpower to the electric motor of the l0 machine;

Fig. 4 is a longitudinal sectional elevational view of the motor andpower transmission mechanism enclosed -by a flame-proof casing;

Fig. 5 is a sectional view taken on the line 5 5 15 of Fig. 4, lookingin-the direction of the arrows;

Fig. 6 is a sectional plan view of the drilling machine including theair circulating mechanism and the heat radiator `for the electric motor;

Fig. 7 is a fragmentary sectional elevation of 90 the switch mechanismand the mechanism for effecting the operation thereof manually to closedposition and automatically to open position;

Fig. 8 is a sectional view taken on the line 8 8 of Fig. 7, looking inthe direction of the arrows, 25 and showing the relative positions ofthe switch operating handle and the switch yoke when the switch isclosed;

Fig. 9 is a view similar to Fig-i8, but showing the relative positionsof the switch operating hana dle and switch yoke when the switch is inopen position; I

Fig. 10 is a sectional view taken on the line lli-Ilot Fig. '7, lookingin the direction of the aITOWS; 3

Fig. 11 is a sectional view taken on the line Il ll of Flg.8;

Fig. 12 is a sectional view similar to Fig. '7, with certain partsbroken away to show more clearly the elements of the switch mechanism;

Fig. 13 is a wiring diagram to illustrate the electrical connectionsfrom the source ofpower to the motor and the electric switch; and

Fig. 14 is a view similar to Fig. l0, but showing the electric switch inclosed position.

Referring more particularly to the drawings, it will be observed thatthe drilling machine shown in plan in Fig. 1 comprises a motor, powertransmission mechanism and an electric controlling switch very compactlyarranged in a flame-proof 50 casing as shown in Fig. 6. The casing orhousing comprises a plurality of compartments detachably connected andarranged and designed for maximum compactness and minimum weight tofacilitate handling of the machine during operation. As shown in Fig. 6,A designates the motor compartment. B the power transmissioncompartment, and C the motor switch compartment. The casing or housingcomprising the three compartments or sections A, B and C is preferablyconstructed except the motor field frame by an assembly oi' castingsoffmagnesium-aluminum alloy which has the advantage of being very lightin weight, easily machined, and having high thercylindrical radiator i9designated By means of cap screws 23 spaced circumferentially around theflange lili, the latter together with the cover 22 may be detachablysecured to the end lli of the radiator i9. Y

It should he particularly noted that the cover 22 is provided with a.cylindrical inwardly extending flange M2 to fit against the annularshoulder i3 with its inner surface iiush with the inner cylindricalsurface of the radiator I9 which also serves as a casing for the motoras herein-s after more fully explained. The flange ||2 is of suiilcientlength to effect a flame-proof closure for the end iii of the casing |9because of the length of the tortuous passageway between the interior ofthe casing and the outside atmosphere. Consequently, when the drillingmachine is used ina gaseous mine and there should be anv explosion of agaseous mixture within the casing no flame can reach the atmosphereoutside ci' the casing even though there should be a gaseous passagewayor crevice along the annular spaces between the ilange |l2 and the endof the radiator iii. As will appear more fully hereinafter, all of theparts enclosing the motor, power transmission mechanism and the switchare so assembled as to provide tortuous surfaces of suiiicient length tocool ignited gases before a flame can reach the atmosphere outside ofthe enclosure.

As shown in Figs, e and 5 the compartment E; is provided with flangestid and H5 similar to flanges il@ and M2 respectively. The cornpartument B is detachably secured to the compartment A by means ofcircurnierentially spaced screws i lo. A {dame-proof connection betweenthe compartment B and the compartment A is thus provided with the innersurface of the ange |65 iiush with the inner surface of the motorcasing.

The compartment B comprises two sections 3&5 and ii'l, the latter beingprovided with a cylindrical ilange lll and a peripheral flange il'ldetachably secured to the section 34 hy means or the circumierentiallyspaced screws i i8 to form a flame-proof connection between the sections3G and lll similar to the flame-proof connections at lili-H5 and Elli,M2.

The motor compartment A is provided with screw-threaded covers |36, |161threaded at 'dit and t? respectively into the section 34 as shown inFig. e. -When these covers are closed theyr may be locked in closedposition by means of the seals shown at |06 and |31 in `Figi. 2. Whenthese seals are broken a Spanner wrench may loe used to open the coversto provide access to the brushes |103 and lila of the *electric motor itas shown in Fig. The screw threads at di and when the covers are closedaiord alsace? tortuous lines of contact of suiiicient length to mairethe covers iBS and |31 flame-proof between the interior oi the casingand the exterior atmosphere.

In a tubular extension |31 of the section ||1 of the compartment B ismounted on the roller thrust bearings 40 and 4|)a a shaft 31 which ispreferably hollow to lessen the weight of the drilling machine Whilebeing manually supported for operation. Between the shaft 31 and thedrill socket 21 which is mounted at the outer end of the hollow shaft 31is an annular collar |38 to provide an annular seat for the ring 4|which is held in place against such annular seat when the inner race ofthe roller thrust bearing 40 is secured to the outer surface of thehollow shaft 31 as shown in Fig. 4. By means of a resilient snap ring4|c a ring shaped plate 4|b is held against an annular seat in the outerend of the tubular support |31 with the inner edge of the ring Mb spacedfrom the peripheral surface of the collar |38 but in contact with therear end of the annular surface of the drill socket diV as shown in Fig.4. When the drill socket rotates the ring 4 |0- rotates with it but thisring does not engage either the ring Mb or the tubular support |31 sinceit is spaced from both of them. This arrangement provides not noly aseal to prevent the ingress of coal dust or other material into .theinterior of the compartment B but also affords a tortuous passagewaybetween the interior of the support |31 and the exterior atmosphere ofsuiiicient length to serve as a dame-prooi closure in a gaseous mineduring operation of the drilling machine. The outer end of the hollowshaft 3l may, if desired, he entirely closed at 63S. The inner end isscrewthreaded to receive the screw plug 38 which is provided with a head3Ba which is so constructed as to enable the lock washer 39 to cooperatetherewith and with the hub of the gear 36 to lock the screw plug 38securely to the hollow shaft 31 to rotate therewith and with the gear dowhich is keyed at 36 to the hollow shaft 31.

IThe outer races of the roller thrust hearings 40 and tiill iit againstannular shoulders 4Gb and idc as shown in Fig. 4. The inner race of theroller thrust hearing l is secured to the outer surface of the hollowshaft 31 in position for one end of the huh of the gear 36 to abutagainst the same. it will thus be seen that the screw plug 3S and. theloclr washer mechanism mounted thereon and associated with the hub ofthe gear 36, lock the latter against longitudinal displacement relativeto the hollow shaft 31. The thrust bearings serve to resist longitudinaldisplacement of the drill socket relative to the tubular support |l3iboth when the drill is fed into the mine vein and when it is pulled outof the drill hole.

By referring to Figs. e and 6, it will he seen that the drill socket ofthe shaft 31 is axially alined with the tubular armature shaft 29 whichis mounted :for rotation in the ball hearing 28 and the section 34 ofthe compartment E. The shaft dii on which the armature of the motor ismounted is made hollow throughout almost its entire length so as toassist in reducing the weight of the drilling machine. One end of thishollow Shaft is screw-threaded to receive the screwthreaded extension30a while the extension 46 at the other end may be solid and integralwith the hollow shaft as shown in Fig. 4. The extensions Sile and doserve respectively as shafts for the pinion 3U and the fan i5hereinafter more fully described.

Mounted on the shaft 29 is a collar 29 adjacent to an annular flange |48on the outer side of which there is located 'a washer |4| between thehub of the collar 29l and the inner race of the ball bearing 28. Thisarrangement serves as a flame-proof connection between the interiorchamber in the compartment A and the interior chamber in the compartmentB. If the flameproof connection at |48 is omitted, reliance may be hadon the name-proof connection at 4|* but itis preferred to use both ofthe name-prooi' connections shown in Fig. 4 at |48 `and 4I so thatdouble assurance may be had that any flame produced by an explosion of agaseous mixture in the compartment A will not find its way through thecompartment B to the outside atmos' phere. It will also be noted thatthe hub of the ring collarv 29 serves to space the motor armature in apredetermined position relative to the section 34 of the compartment B.Inasmuch as the end thrust on the armature shaft of the motorr is smallduring rotation, the ball bearings 2| and 28 held'in place as shown inFig. 4 are suiiicient to prevent longitudinal movement of the armatureshaft 29 relative to the enclosing casing. The ball bearing 2| ismounted ln a cup shaped seat at the center of the inner side of thecover 22. The ball bearing 28 is mounted in a cup shaped seat 34 and itis held in place by the resilient snap ring 28'. The brush holdersupport 29b is ring shaped and secured to the bosses 29 as shown in Fig.6, in spaced relation to the collar 29* which, together with the washer|4|, rotates with the hollow shaft 29. The inner race of the ballbearing 28 fits against an annular seat formed by the collar 28 mountedat the inner end of the pinion 30 on the pinion shaft 38' which isscrew-threaded into the hollow shaft 29 as shown in Fig. 4.

The .pinion 38 meshes with a gear 3| mounte on a shaft 32 the ends ofwhich are mounted on the ball bearings 33, 33. The shaft 32 carries apinion 35 which meshes with a gear 36. It will thus be seen thatreduction gearing is provided in the section 34 of the compartment B toserve as power transmission mechanism between the armature shaft 29 andthe hollow tool socket shaft 31 with the shafts 29 and 31 in axiallalinement l with each other.

In Figs. 4 and 6 the tool socket 21 is shown as being provided withinterior lugs |36, |38 which are adapted to cooperate with the drillshank to hold the latter in position in the socket during the drillingoperation. 'I'he lugs |36 may be formed of rivet heads welded orotherwise secured in place as shown in Fig. 4. In Fig. 2 a modified formof drill socket is shown at |34 for receiving the standard type oftapered drill shanks.

In order to support the drilling machine manu-7, ally during operationwith its center of gravity back of the alined hollow handles 41 and |32or away from the drill socket 21, said.I handles are connected to thecasing of the machine so as to extend in opposite directions as shown inFig. l at right angles to the axis of the motor shaft and of the drill.The handle |32 as shown in Fig. 6

` is screw-threaded into the socket |33 of comhandle |32 remains rigidlyconnected tothe supporting casing but the handle 41 is mounted forlimited rotation.

Mounted in the tubular extension 48 of the compartment C is a bushing 52to serve as a journal bearing for the cup shaped sleeve 49 which issecured by means of the pin 50 to the inner end portion of the hollowhandle 41. The bushing 52 is secured to the tubular extension 48 bymeans of the pin shown at 48. A portion of the bushing 52 extendsinwardly to form ixed abutments 52* and 52h as shown in Figs. 8 and 9,which abutm'ents'are stationary relative to the supporting casing orirame of the drilling machine.

The outer end of the sleeve 49 is provided with an annular ange 49nwhich is adapted to abut against the outer end of the bushing 52 asshown in Fig. 6. A retaining washer H9* and a snap ring ||9 serve tohold the annular flange 49 in its position against the outer end of thebushing 52 as shown in Fig. 6.

'I'he outer end of the tubular support 48 is recessed not only toprovide annular seats for the washer ||9l and the snap ring 9 but alsothe inner end of the coll spring 51 which inner end is secured at 58 tothe tubular support 48 as shown in Fig. 2. The outer end of the spring51 is secured at 58 to the tubular handle 41 as shown in Figs. 2 and 6.'Ihe inner end 5| of the sleeve 49 is provided with an extension 49'which is provided with a spring seat 5|* and a movable abutment 5|b.When theihandle 41 is released the spring 51 acts to move the abutmentcarrier 49 to a position shown in Fig. 9.

Projecting axially from the center of the plate 5| as shown in Fig. 6,is a bearing 54 about which is coiled the intermediate portion of thespring 68, one end of which at iii)b rests against the seat 5| and theother end of which at 60 bears against the yoke 53 one end of which isjournaled on the bearing 54 and the other end of which is provided witha shaft 54a which is journaled in the bearing 55 as shown in Fig. 6. Theshaft 54 is in axial alinement with the bearing 54.

The yoke 53 is connected to electric switch mechanism for controllingthe starting and stopping of the electric motor by means of the circuitsand connections diagrammatically illustrated in Fig. 13. When the handle41 is turned in one direction the switch will be closed and the motorstarted to operate the drill 4| while the drilling machine is supportedmanually and fed manually into the coal vein. The rotatlonvof the handle41 to close the switch places such tension in the spring 51 that whenthe handle 41 is released by the operator the spring 51 will actautomatically to restore the switch to its open position and therebyeffect stopping of the motor.

Inasmuch as it is desirable to open the switch with a snap a'ction oreiect very quick separation of the contacts of the electric switch inorder 'to reduce the arcing to a minimum when the circuit of theelectric motor is broken, compactly arranged automatic switch operatingmechanism is mounted in the compartment C and connected to Ithe handle41 as shown in Figs. 6, 8 and 9. The switch mechanism is mounted betweenblocks of insulating material 11 and 93 which are secured to the bosses96a and 99 by means of the screw-threaded ends of the cap screws 96 and98 and the insulating spacing tubes 91 and 66 as shown in Figs. 10, 11and 14.

The spacers 66 may be integral with the insulating block 11 and eachprovided with a depending support 66 provided with alined openings forreceiving the inner ends of laterally projecting bearings 65, 65 whichmay be pinned to the support 66' as indicated at 65*L in Fig. 12.

As shown in Figs. 10, 1l, 12 and 14, insulating blocks 6| are providedwith upwardly opening slots or recesses 64 to lit over the bearings 65from the underside of the latter. The insulating blocks 6| are rigidlyconnected by the transverse insulating cross-piece 6|'. Between theblocks 6| and parallel to the crosspiece 6|' is mounted a transverse pin69 having a groove 10 intermediate its ends for receiving the lower end10' of thespring 88, the upper end of which is hooked at 1| through theopening 12 at the upper central portion of the yoke 53.

Each of the insulating blocks 6| carries a metallio strip or iinger 62the lower end of which ls pinned at 83 to the copper contact 63. At theupper end oi each metal strip 62 is a square hole adapted to iit looselyover the squared head 18 of a screw inserted in the upper portion of theblock 6i as shown in Figs. l0 and 14. This arrangement prevents thecontact carrying strips or fingers 52 from swiveling in its own planebut a limited movement of the strip 62 transversely ol its own plane ispermitted to secure a wiping action of the contact 63 against the metalplate 13 when the switch is moved from its open position in Fig. 10 toits closed position in Fig. 14.

A pin 19 secured to each block 6| projects through a hole in the strip62 intermediate its ends. Each pin 19 is provided with a collar.80 witha spring 8| between the same and the outer surface of the strip 62 asshown in Figs. 10 and 14. A cotter pin 82 holds the collar 80 in piace.When the block 6| is moved to the position shown in Fig. 14 the spring8| holds the contact 63 yieldingly against the metal plate 13. As shownin Figs. l and 14, the metal plate 13 is secured by means of the capscrew 14 to the base block 16 of insulating material which may beintegral with the insulating block 11.

By referring to Fig. 12, it will be seen that spaced-apart electricterminals may be aiiorded by the metal plates 15, 15 secured to themetal plates 13, 13 by means of the screws 15', 15. Electric terminals62B, 62a are riveted to the contact carrying strips 62 as shown at 62D,62". As shown in Fig. 13, the switch is two-pole in that one electricconductor extends through the contacts 63, 13 and another conductorextends through the contacts 63', 13', said conductors beingrespectively connected to the supply mains.

In order to minimize arcing during operation of the switch mechanism,there is mounted between the insulating blocks 11 and 93 within thespace between the base blocks 16, 16, a blow-out coil 84 having an ironcore 84B the ends of which project through openings into insulatingblocks 84h, 84b so as to occupy positions closely adjacent to the pointsof engagement between the contacts 63 and the plates 13. As shown inFig. 13 the winding of the blow-out coil 84 is connected in the motorcircuit and in series with the two sides of the double-pole switch. Whenthe switch is open the blow-out coil acts to lengthen the arcs betweenthe contact 63 and the plate 13 aiding the disruption of such arcs.

As a precaution against the burning of any of the parts when such arcsare formed upon the breaking of the circuitsiat the switch contacts inthe compartment C, plates |35, |35 of asbestos or other non-inhammablematerial are secured at |45, |45 to the outer surfaces of the baseblocks 16 at the sides of the switch mechanism as shown in Fig. 12. Thesecuring means at |45, |45 may be screws extending into the blocks 16 asshown in Figs. 10 and 14. The end blocks 84h, 84b of the blow-out coilare also preferably made of asbestos or other non-inflammable material.

A safety fuse 9| is mounted between clips 92, 92 and connected in themotor circuit as shown in Fig. 13.. The compartment C in which theswitch mechanism is mounted is provided with a cover screw-threaded toclosed position and sealed in closed position as illustrated at |20 inFig. 6. Access may be had to the interior of the compartment C forrenewal of the blown-out fuse 9| by removing the cover |05 but not untilthe seal |20 has been broken.

Secured to the insulating block 93 by means of the screws |0I, |0| is aplate of insulating material provided with upper and lower extensions|02 and |03 at right angles to the block 93 and extending across theouter ends of the clips 92, 92`as shown in Fig. 1 so as to prevent anypossibility of grounding of the clips 92, 92 through the heads of thescrews 96, 98 to the metal frame or casing of the drilling machine.

A connector |04 as shown in Fig. ll for the conductor |26 shown in Fig.13 may be mounted bach of a curved portion |43 of the shield |44 forprotection thereby.

In order properly to space the ends of the iron core 94 of the blow-outcoil 84 from the switch contacts 63, 13 a retaining block 95 ofinsulating material is riveted at 94 to the inner surface of theinsulating block 93 as shown in Fig. 1l. The lower corners of the block95 are suitably notched to fit over the beveled upper edges 84c of therectangular end insulating blocks 84|. The latter are also clamped bymeans of the screws 96 and 98 between the insulating blocks 93 and 11.

It should be particularly noted that when the cover |05 is removed theentire switch unit may be removed and taken apart for the purpose ofrepair or replacement. This is particularly true with respect to thecontact carrying mechanism because the open slots 64 permit theinsulating block 6| together with the crosspiece 6| to be removed fromthe bearings 65, 65 against the action of the spring 68. If desired, thecontact carrier may be readily detached from the hook at the lower endof the spring 68. When the retaining ring ||9 shown in Fig. 1 is removedthe handle 41 may be removed from the journal bearnig 52 thusdisconnecting the handle from the yoke 53 and permitting the removal ofthe latter from the bearing 55.

When all of the parts of the drilling machine are in assembled relationready for operation, the electric switch may be closed to effectstarting of the motor by rota-tion of the handle 41 against the actionof the spring 51 in an anticlockwise direction as viewed in Fig. 9. Whenthe switch is open the yoke 53 occupies the position shown in Fig. 9 orthe position shown in iull lines in Fig. 1l.

When the handle 41 is rotated in an anticlockwise direction as viewed inFig. 9 the abut-,.1

ment 5|b will engage the yoke 53 to swing the same from its full lineposition shown in Fig. 11 toward its dotted line position. In doing so,the outer central portion of the yoke 53 engages the free end of thespring clip |2| which is secured to the inner surface of the compartmentC as shown in Figs. 7 and l1. However, the yoke .53 clears the springclip |2I by the time that the spring 88 moves to a position to the leftof the axis of the bearing as viewed in Fig. 11 whereupon the spring 69is free to act to eiect closure of both of the sets of contactsdesignated 63, 13 and 63', 13' in Fig. 13. When the switch is closed theyoke 53 is held against the fixed abutment 52n with the abutment 5|hheld manually against the other side of the yoke 53 as shown in Fig. 8.Furthermore, when the switch is closed the spring 60 has one 'arm 60hresting against the seat 5|n and the other arm 50l engaging that side ofthe yoke 53 remote from the abutment When it is desired to open theswitch the handle 41 is` released whereupon the stored tension in thespring 51 will act automatically to move the carrier 49' in a clockwisedirection as viewed in Fig. 9 thereby continuing to move the abutment5|'J away from the yoke 53. The yoke 53 moves through asmall angle to aposition in engagement with the spring clip |2| due to tension in spring00. At such time the spring 00 does not have suiiicient tension to movethe yoke 53 past the clip |2|. In other words, the clip |2| preventscontinued movement of the yoke 53 until a predetermined amount oftension is stored in the spring 60. The purpose of the retarding actionof the spring clip |2| is to hold the yoke 53 in such position that thespring 50 may be at the left of the axis of the bearings 65 so that theswitch will be held positively closed until it is ready to open with asnap action. That .is to say, in order to prevent initial movement ofthe handle 41 towards switch opening position from causing the contacts53 and 63' from separating from the plates 13, 13' the spring clip |2|causes the spring 60 to hold the switch positively closed therebypreventing arcing which would occur when the contacts 63, 03' are movedonly a short distance from the plates 13, 'I3'. As rotation of thehandle 41 continues in a clockwise direction as viewed in Fig. 8, theabutment 5|b moves farther away 'om the yoke 53, but the latter beingheld by the spring clip |2| causes incrcasingtension to be stored in thespring 60 until such tension is sufiicient to overcome the holdingyeffect of the spring clip |2|. Then the spring 60 moves the yoke 53from u nder the spring clip |2| whereupon the spring 69 moves to theright of the center of the bearing 05 as viewed in Fig. 11, whereuponthe contacts 63, 03' would be suddenly and quickly withdrawn from thecontact plates 13, 13'. When the switch is in open position the yoke 53will rest against the abutment 52b as shown in Fig. 9 and the crosspiece6| of the switch contact carrier will abut against the back of theinsulating block 95 as shown in Fig. l1;

Fig. 13 shows diagrammatically the circuits and connections for theelectric drill motor and the switch for controlling the same. Theterminal l hook |28 may be connected to a trolley wire in a mine toserve as the connector to the positive supply main |21 which isconnected to the plate 13. The hook`|22 may be attached to the rail |3|of the mine track to serve as the connector to the negative supply main|23 which is connected to the contact plate 13. The motor is preferablycompound wound so that it will not race under substantially no load andyet be capable oi.' withstanding heavy overloads without overheating.

When the switch is closed the motor circuit may be traced in Fig, 13 tothe conductor |21 through contacts 13', 63', fuse 9|, conductor |25,series motor winding 85, motor armature I4, conductor |25, blow-out coil04, contacts 03, 13 and thence to the negative conductor |23. The shuntfield coil 35 is also energized as it is shunted across series winding05 and armature |4 In order to protect the operator of the drillingmachine the casing or frame thereof is grounded by a conductor |30connected at its outer free end to the rail |3| and at its inner end tothe frame or casing of the machine as illustrated diagrammatically at|29 in Fig. 13. This grounding connection may be effected by connectingthe conductor |30 to the head of the screw 95 as shown in Fig. 2, whichscrew is of metal and in metallic contact with the metal frame of themachine.

It should be particularly noted that the cable 00 carrying the threeconductors |23, |21 and |30 is connected by means of the connectorsshown in Fig. 3 to the compartment C with an airtight nt so that no gascan enter the compartment C or escape therefrom either through theconnector or the cable, the latter being impervious to air since it iscomposed of insulating material with the three separate wires imbeddedtherein i'or insulation from each other.

The connector shown in Fig. 3 comprises a tube 83 which isscrew-threaded into the socket 90 which may be integral with the casingof comlpartment C. By screwing the tube 00 into the screw-threadedportion 09 of the socket 90 it engages the packing gland b which islocated above the packing 90c in the lower cup portion of the socket 90.By means oi' a split sheath 01 surrounding the cable 90 and extendinginto the `tubular member 39, and a clamp 90|, the cable may be securedagainst longitudinal movement relatively to the housing oi.' thecompartment C. After the connector has been assembled and the cable 09locked in adjusted position relative to the housing, a seal 9|* may beused as shown in Fig. 3 to prevent tampering with the connector.

One of the principal features oi' the construction shown in Figs. 5 and6 is the provision of means for effecting internal air circulation aboutthe motor amature for the purpose of cooling the motor or preventingoverheating thereof.- A multi-stepbladed centrifugal fan |5isconnectedto the shaft 46 to rotate therewith immediately inside of the cover 22.Batlle vplates I0, |6, each having the shape of a segment of a cylinderas shown in Fig. 5 and composed of iiber or other light insulatingmaterial, are mounted between the pole pieces 24 and between the fieldcoils 25. At those ends of the baiiie plates 6 near the cover 22 aremounted the plane baille plates IiiB which are secured to the inside ofthe cover 22 by means of brackets |49, and the rivets |61. The inneredges of the baille plates 5'L are in such positions that they willclear the outer periphery of the fan i5 when the cover 22 is removed.

It will be seen by referring to Figs. 5 and 6 that the baille platesI0"L co-operate with the pole pieces 24 and the windings 25 thereon toclose the outer ends of the spaces between the motor armature and thebaille I6 so that when the fan I5 rotates a circulation of air onopposite sides of the motor will be produced in the direction of thearrows |1 and i0. 'I'hat is to say, when. the fan rotates the baiiie 6co-operates with the pole pieces 24 and the windings 25 thereon tocompel the air to move into the intake openings of the fan within theperiphery thereof so that the air will be thrown out by centrifugalforce for inward circulation as indicated by the arrows I9, thus causingthe air which has absorbed heat from the armature. to come in contactwith the inner surface of the cylindrical radiator I9. The

outer surface is provided with circumferential ribs 20 .to increase theouter heat radiating surface.

Theradiator i9 constitutes the field frame of the electric motor and istherefore made of iron or steel but the cover 22 and the various otherparts of the casing or frame of the machine together with the handles 41and |32 are preferably made of a light alloy, such as magnesium-aluminumheat-treated. In a drilling machine of the construction shown anddescribed having a compound wound electric motor oL'one and one-half totwo horsepower operated at an applied voltage of 250, the weight of theentire drilling machine, excluding the drill, need be no greater than 38pounds. The center of gravity in a drilling machine is located back ofthe handles, or away from the drill socket, to assist incounterbalancing the weight of the auger while a single operatorsupports the drilling machine during operation and by leaning against itor pushing it feeds the drill into a coal vein.

One of the handles is rotated by the operator who effects starting ofthe drilling machine and when this handle is released the motor isautomatically stopped with a minimum amount or arcing at the switchcontacts. Notwithstanding the operation oithe interior controllingswitch from without the machine the enclosing structure is entirelyflame-proof and the electrically operated drill is therefore permissiblefor operation in gaseous mines. All detachable parts by the removal ofwhich access could be had to the interior of the enclosing structure arepreferably locked and sealed against opening by the operator while usingthe machine for operation in a gaseous mine. It will also be noted thatthe complete closure of the motor, power transmission mechanism and themotor controlling switch prevents access of dust and dirt to theinteriorn relatively movable parts.

Obviously those skilled in the art may make various changes in thedetails and arrangement of parts without departing from the spirit andscope of the invention as defined by the claims hereto appended, and Itherefore wish not to be restricted to the precise construction hereindisclosed.

Having thus described and shown an embodiment of my invention, what Idesire to secure by Letters Patent of the United States is:

l. In a drilling machine, the combination with an electric motor, ofmeans for controlling the operation of said motor, communicatingenclosures for said motor and said controlling means, means affording acorrugated exterior surface for that portion of said motor enclosuresurrounding the armature of the motor and constituting the field framethereof, a fan connected to one end of the motor armature, and meanscomprising baille plates serving as partitions between said armature andthe interior of said casing to provide chambers parallel to the motoraxis, said plates being so constructed and arranged as to cooperate withsaid fan to direct air rst across the face of said armature and thenacross the interior of said casing to dissipate heat generated by saidmotor, and to circulate air within said controller enclosure. y

2. In a drilling machine, the combination with an electric motor, of anenclosure for said motor, means affording a radiating exterior surfacefor that portion of said enclosure surrounding the i armature of themotor and constituting the eid frame thereof, a ian connected to one endof the motor armature, and means comprising baille plates having theiredges extending along the field coils of said motor and serving aspartitions between said armature and the interior of said casing toprovide chambers parallel to the motor axis, said plates being soconstructed and arranged as to cooperate with said fan to direct airnrst across the face of said armature and then across the faoesof saidfield coils and the interior of said casing to dissipate heat generatedby said motor.

3. In a portable tool, the combination with a ame proof casing, of amotor in said casing, operating mechanism driven by said motor, a

switch for controlling said motor, a iiame proof casing for said switch,said two casings having communication whereby the air in each maycirculate in the other, and fan means driven by said motor forcirculating the air in both of said casings.

4. In apparatus for use in a gaseous mine, the combination with a casingformed into a motor compartment and a gear compartment by a partition,of a motor in said motor compartment, gears in said gear compartment, ashaft extending between said motor and said gears, a drive shaftextending from said casing and driven by said gears, a flame sealbetween said drive shaft and said casing to provide for rotation of saidshaft while restricting egress of any flame from said casing, and asecond flame seal between said first named shaft and said partition.

5. In mining apparatus, the combination with a flame proof casing,partition means forming said casing into motor, gear and switchcompartments, a motor in said motor compartment, gears in said gearcompartment and a switch in said switch compartment, a pair of rotatableshafts, one extending from said gear compartment and operated by saidgears and the other extending from said switch compartment andcontrolling said switch, ilame seals for each of said shafts to providefor their turning While resisting egress of any iiame from said casing,means connecting said motor and gears, and electrical circuitsconnecting said switch and motor.

6. In a mining drill, the combination with a flame proof casing, of amotor in said casing, a drill shaft extending from said casing,reduction means interconnecting said motor and drill shaft, a motorcontrol switch in said casing, an operating shaft for said switchextending into said casing, a flame seal forsaid drill shaft, and a:flame seal for said switch operating shaft, said name seals providingfor rotation of 'said shafts while resisting the egress of any iiamefrom said casing.

7. In a drilling machine, the combination with an electric motor, of acasing for said electric motor, said motor including a stationary eldstructure attached to said casing and a rotating armature, a fan rotorconnected to said armature to be rotated thereby, baiiie means in saidcasing constructed and arranged to guide circulating air across saidarmature in one direction and in a reverse direction across the casingin terior, said baffle means including a portion adjacent the ian rotorto provide a restricted fan inlet leading to said fan rotor throughwhich fan rotor substantially all of the circulated air must pass.

ROBERT'K. JEFFREY.

